Eagerly verify Sample values are float-convertible

prometheus_client/metrics_core.py

@@ -257,10 +257,13 @@ def add_metric(self, labels, buckets, gsum_value, timestamp=None):
                 dict(list(zip(self._labelnames, labels)) + [('le', bucket)]),
                 value, timestamp))
         # +Inf is last and provides the count value.
-        self.samples.extend([
+        self.samples.append(
             Sample(self.name + '_gcount', dict(zip(self._labelnames, labels)), buckets[-1][1], timestamp),
-            Sample(self.name + '_gsum', dict(zip(self._labelnames, labels)), gsum_value, timestamp),
-        ])
+        )
+        if gsum_value is not None:
+            self.samples.append(
+                Sample(self.name + '_gsum', dict(zip(self._labelnames, labels)), gsum_value, timestamp),
+            )
 
 
 class InfoMetricFamily(Metric):

prometheus_client/openmetrics/exposition.py

@@ -8,6 +8,13 @@
 """Content type of the latest OpenMetrics text format"""
 
 
+def _to_openmetrics_value(value):
+    # Openmetrics distinguishes integers and floats with different text representations.
+    if type(value) == int:
+        return str(value)
+    return floatToGoString(value)
+
+
 def generate_latest(registry):
     '''Returns the metrics from the registry in latest text format as a string.'''
     output = []
@@ -37,13 +44,13 @@ def generate_latest(registry):
                     if s.exemplar.timestamp is not None:
                         exemplarstr = ' # {0} {1} {2}'.format(
                             labels,
-                            floatToGoString(s.exemplar.value),
+                            _to_openmetrics_value(s.exemplar.value),
                             s.exemplar.timestamp,
                         )
                     else:
                         exemplarstr = ' # {0} {1}'.format(
                             labels,
-                            floatToGoString(s.exemplar.value),
+                            _to_openmetrics_value(s.exemplar.value),
                         )
                 else:
                     exemplarstr = ''
@@ -53,7 +60,7 @@ def generate_latest(registry):
                 output.append('{0}{1} {2}{3}{4}\n'.format(
                     s.name,
                     labelstr,
-                    floatToGoString(s.value),
+                    _to_openmetrics_value(s.value),
                     timestamp,
                     exemplarstr,
                 ))

prometheus_client/samples.py

@@ -36,8 +36,17 @@ def __gt__(self, other):
 # Timestamp can be a float containing a unixtime in seconds,
 # a Timestamp object, or None.
 # Exemplar can be an Exemplar object, or None.
-Sample = namedtuple('Sample', ['name', 'labels', 'value', 'timestamp', 'exemplar'])
-Sample.__new__.__defaults__ = (None, None)
+sample = namedtuple('Sample', ['name', 'labels', 'value', 'timestamp', 'exemplar'])
+
+
+# Wrap the namedtuple to provide eager type-checking that value is a float.
+def Sample(name, labels, value, timestamp=None, exemplar=None):
+    # Preserve ints, convert anything else to float.
+    if type(value) != int:
+        value = float(value)
+
+    return sample(name, labels, value, timestamp, exemplar)
+
 
 Exemplar = namedtuple('Exemplar', ['labels', 'value', 'timestamp'])
 Exemplar.__new__.__defaults__ = (None,)

tests/openmetrics/test_exposition.py

@@ -122,11 +122,11 @@ def collect(self):
         self.registry.register(MyCollector())
         self.assertEqual(b"""# HELP hh help
 # TYPE hh histogram
-hh_bucket{le="1"} 0.0 # {a="b"} 0.5
-hh_bucket{le="2"} 0.0 # {le="7"} 0.5 12
-hh_bucket{le="3"} 0.0 123 # {a="b"} 2.5 12
-hh_bucket{le="4"} 0.0 # {a="\\n\\"\\\\"} 3.5
-hh_bucket{le="+Inf"} 0.0
+hh_bucket{le="1"} 0 # {a="b"} 0.5
+hh_bucket{le="2"} 0 # {le="7"} 0.5 12
+hh_bucket{le="3"} 0 123 # {a="b"} 2.5 12
+hh_bucket{le="4"} 0 # {a="\\n\\"\\\\"} 3.5
+hh_bucket{le="+Inf"} 0
 # EOF
 """, generate_latest(self.registry))
 
@@ -159,10 +159,10 @@ def test_gaugehistogram(self):
             GaugeHistogramMetricFamily('gh', 'help', buckets=[('1.0', 4), ('+Inf', (5))], gsum_value=7))
         self.assertEqual(b"""# HELP gh help
 # TYPE gh gaugehistogram
-gh_bucket{le="1.0"} 4.0
-gh_bucket{le="+Inf"} 5.0
-gh_gcount 5.0
-gh_gsum 7.0
+gh_bucket{le="1.0"} 4
+gh_bucket{le="+Inf"} 5
+gh_gcount 5
+gh_gsum 7
 # EOF
 """, generate_latest(self.registry))
 
@@ -171,10 +171,10 @@ def test_gaugehistogram_negative_buckets(self):
             GaugeHistogramMetricFamily('gh', 'help', buckets=[('-1.0', 4), ('+Inf', (5))], gsum_value=-7))
         self.assertEqual(b"""# HELP gh help
 # TYPE gh gaugehistogram
-gh_bucket{le="-1.0"} 4.0
-gh_bucket{le="+Inf"} 5.0
-gh_gcount 5.0
-gh_gsum -7.0
+gh_bucket{le="-1.0"} 4
+gh_bucket{le="+Inf"} 5
+gh_gcount 5
+gh_gsum -7
 # EOF
 """, generate_latest(self.registry))
 
@@ -192,8 +192,8 @@ def test_enum(self):
         i.labels('c', 'd').state('bar')
         self.assertEqual(b"""# HELP ee An enum
 # TYPE ee stateset
-ee{a="c",b="d",ee="foo"} 0.0
-ee{a="c",b="d",ee="bar"} 1.0
+ee{a="c",b="d",ee="foo"} 0
+ee{a="c",b="d",ee="bar"} 1
 # EOF
 """, generate_latest(self.registry))
 
@@ -250,12 +250,12 @@ def collect(self):
         self.registry.register(MyCollector())
         self.assertEqual(b"""# HELP ts help
 # TYPE ts unknown
-ts{foo="a"} 0.0 123.456
-ts{foo="b"} 0.0 -123.456
-ts{foo="c"} 0.0 123
-ts{foo="d"} 0.0 123.456000000
-ts{foo="e"} 0.0 123.000456000
-ts{foo="f"} 0.0 123.000000456
+ts{foo="a"} 0 123.456
+ts{foo="b"} 0 -123.456
+ts{foo="c"} 0 123
+ts{foo="d"} 0 123.456000000
+ts{foo="e"} 0 123.000456000
+ts{foo="f"} 0 123.000000456
 # EOF
 """, generate_latest(self.registry))
 

tests/test_exposition.py

@@ -348,17 +348,6 @@ def collect(self):
         return [self.metric_family]
 
 
-def _expect_metric_exception(registry, expected_error):
-    try:
-        generate_latest(registry)
-    except expected_error as exception:
-        assert isinstance(exception.args[-1], core.Metric)
-        # Got a valid error as expected, return quietly
-        return
-
-    raise RuntimeError('Expected exception not raised')
-
-
 @pytest.mark.parametrize('MetricFamily', [
     core.CounterMetricFamily,
     core.GaugeMetricFamily,
@@ -373,7 +362,12 @@ def _expect_metric_exception(registry, expected_error):
 def test_basic_metric_families(registry, MetricFamily, value, error):
     metric_family = MetricFamily(MetricFamily.__name__, 'help')
     registry.register(Collector(metric_family, value))
-    _expect_metric_exception(registry, error)
+    try:
+        generate_latest(registry)
+    except error as exception: 
+        # Got a valid error as expected, return quietly
+        return
+    raise RuntimeError('Expected exception not raised')
 
 
 @pytest.mark.parametrize('count_value,sum_value,error', [
@@ -389,14 +383,18 @@ def test_basic_metric_families(registry, MetricFamily, value, error):
 def test_summary_metric_family(registry, count_value, sum_value, error):
     metric_family = core.SummaryMetricFamily('summary', 'help')
     registry.register(Collector(metric_family, count_value, sum_value))
-    _expect_metric_exception(registry, error)
+    try:
+        generate_latest(registry)
+    except error as exception:
+        # Got a valid error as expected, return quietly
+        return
+    raise RuntimeError('Expected exception not raised')
 
 
 @pytest.mark.parametrize('MetricFamily', [
     core.GaugeHistogramMetricFamily,
 ])
 @pytest.mark.parametrize('buckets,sum_value,error', [
-    ([('spam', 0), ('eggs', 0)], None, TypeError),
     ([('spam', 0), ('eggs', None)], 0, TypeError),
     ([('spam', 0), (None, 0)], 0, AttributeError),
     ([('spam', None), ('eggs', 0)], 0, TypeError),
@@ -408,7 +406,12 @@ def test_summary_metric_family(registry, count_value, sum_value, error):
 def test_histogram_metric_families(MetricFamily, registry, buckets, sum_value, error):
     metric_family = MetricFamily(MetricFamily.__name__, 'help')
     registry.register(Collector(metric_family, buckets, sum_value))
-    _expect_metric_exception(registry, error)
+    try:
+        generate_latest(registry)
+    except error as exception:
+        # Got a valid error as expected, return quietly
+        return
+    raise RuntimeError('Expected exception not raised')
 
 
 if __name__ == '__main__':